Electric vehicle

ABSTRACT

An electric vehicle capable of protecting a coupling portion between a wheel and an axle from disturbance. An electric vehicle includes an axle that is a hollow cylindrical shaft passing substantially coaxially through a wheel in a manner extending from both sides of the wheel. A motor shaft is inserted into a hollow portion of the axle substantially coaxially with the axle in a manner extending from both ends of the axle. In this case, a motor is connected to a base end of the motor shaft extending from one end of the axle. Between the wheel and the motor, there are provided a coupling portion for coupling between the one end of the axle and the wheel, and a labyrinth structure for sealing between the wheel and the motor in a manner surrounding the coupling portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 USC 119 to JapanesePatent Application No. 2011-081263 filed Mar. 31, 2011 the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric vehicle in which an outputof a motor is transmitted to an axle through a reduction mechanism,thereby rotating a wheel.

2. Description of Background Art

In the past, various electric vehicles have been proposed in which anoutput of a motor is transmitted to an axle through a reductionmechanism, thereby rotating a wheel.

For example, in JP-A No. H10-89439, there is proposed a structure inwhich a motor, a reduction mechanism, and a wheel are coaxiallyconnected to an axle (a drive shaft) in this order. One end of the driveshaft toward which the motor is located, and the other end toward whichthe wheel is located, are each fastened by a nut.

However, in JP-A No. H10-89439, a motor shaft and the reductionmechanism are disposed on the one side, leading to a weight imbalance.In addition, the nut for fastening the wheel to the drive shaft isexposed to a side surface of the wheel on the other side. For thisreason, the nut might be affected by disturbance such as stonesscattered by the wheel during the operation of an electric vehicle oraccess to the nut by a person such as an occupant.

SUMMARY AND OBJECTS OF THE INVENTION

Accordingly, the present invention has been made in view of the problemsin the related art, and an object of an embodiment of the presentinvention is to provide an electric vehicle in which a coupling portionbetween a wheel and an axle can be protected from disturbance while amotor and a reduction mechanism are disposed in such a manner so as tobe distributed one on each side of the wheel.

In order to accomplish the above-mentioned object, a feature of anembodiment of the present invention is that, in an electric vehicle (10)in which an output of a motor (16) is transmitted to an axle (52)through a reduction mechanism (160) in order to rotate a wheel (90),with the axle (52)being a hollow cylindrical shaft passing substantiallycoaxially through the wheel (90) in a manner extending from both sidesof the wheel (90). The motor (16) has a motor shaft (16 a) inserted intoa hollow portion of the cylindrical shaft (52) substantially coaxiallywith the cylindrical shaft (52) in a manner extending from both ends ofthe cylindrical shaft (52). The motor (16) is connected to a base end ofthe motor shaft (16 a) extending from one end of the cylindrical shaft(52) with the reduction mechanism (160) being connected to a leading endof the motor shaft (16 a) extending from the other end of thecylindrical shaft (52). A coupling portion (192) is provided forcoupling between the one end of the cylindrical shaft (52) and the wheel(90), and a sealing portion (190, 194) is provided for sealing betweenthe wheel (90) and the motor (16) in a manner surrounding the couplingportion (192), are provided between the wheel (90) and the motor (16).

According to an embodiment of the present invention, the couplingportion (192) is composed of a threaded portion formed at the one end ofthe cylindrical shaft (52); and a nut (172) threaded onto the threadedportion for coupling between the wheel (90) and the cylindrical shaft(52).

According to an embodiment of the present invention, a motor case (44)is provided for storing the motor (16); and a first bearing (194) isinserted between the motor case (44) and the wheel (90) in a mannersurrounding the motor shaft (16 a), the cylindrical shaft (52), and thecoupling portion (192). The first bearing (194) relatively rotatablymounts the motor case (44) to the wheel (90).

According to an embodiment of the present invention, a portion (195) ofthe motor case (44) opposite the coupling portion (192) is tapered so asto deviate from the nut (172).

According to an embodiment of the present invention, a motor module (46)is composed of the motor (16) and the motor case (44) with a reductionmechanism module (50) composed of the reduction mechanism (160) and areduction mechanism case (48) for storing the reduction mechanism (160).A second bearing (254) is inserted between the reduction mechanism case(48) and the wheel (90) in a manner surrounding the motor shaft (16 a)and the cylindrical shaft (52). The second bearing (254) relativelyrotatably mounts the reduction mechanism case (48) to the wheel (90).

According to an embodiment of the present invention, a labyrinthstructure (252) is formed between the reduction mechanism case (48) andthe wheel (90) in a manner surrounding the second bearing (254).

According to an embodiment of the present invention, a brake (260) isprovided for braking rotation of the wheel (90). The brake (260) isdisposed in a hollow portion between the labyrinth structure (252)provided between the reduction mechanism case (48) and the wheel (90),and the second bearing (254).

According to an embodiment of the present invention, a third bearing(198, 200) is inserted between the motor case (44) and the motor shaft(16 a). The third bearing (198, 200) relatively rotatably supports themotor case (44) on the motor shaft (16 a) with a sealing being appliedto at least one of the first to third bearings (194, 198, 200, 254).

According to an embodiment of the present invention, the sealing portion(190, 194) is a labyrinth structure (190) formed between the motor case(44) and the wheel (90) in a manner surrounding the first bearing (194),and/or the sealed first bearing (194).

According to an embodiment of the present invention, a hole portion(214) or a bolt head (282) is provided at the leading end of the motorshaft (16 a). The hole portion (214) allows insertion of a screw-driveror a hex wrench.

According to an embodiment of the present invention, the reductionmechanism (160) is provided with a first gear (216) formed at theleading end of the motor shaft (16 a) and a second gear (220) disposedforwardly of the motor shaft (16 a), the second gear (220) engaging withthe first gear (216). A reduction shaft (218) is disposed forwardly ofand substantially parallel to the cylindrical shaft (52) and the motorshaft (16 a), and substantially coaxially connected to the second gear(220). A third gear (222) is formed on the side of the reduction shaft(218) toward the wheel (90) with a fourth gear (224) being substantiallycoaxially connected to the cylindrical shaft (52) on the other end ofthe cylindrical shaft (52), the fourth gear (224) engaging with thethird gear (222). A hole portion (286) or a bolt head (288) is providedat an end of the reduction shaft (218) toward the second gear (220). Thehole portion (286) allows insertion of a screw-driver or a hex wrench.

According to an embodiment of the present invention, a sealing member(232) is inserted between the other end of the cylindrical shaft (52)and the motor shaft (16 a).

According to an embodiment of the present invention, a double-sidedswing arm (14) is provided for supporting the motor shaft (16 a), thecylindrical shaft (52), and the wheel (90) by respectively supportingthe motor (16) and the reduction mechanism (160).

According to an embodiment of the present invention, the motor isconnected to the base end of the motor shaft on one side of the wheel,and on the other side, the reduction mechanism is connected to theleading end of the motor shaft. Thus, weight balance is easily achieved.In addition, between the wheel and the motor, the coupling portioncouples between the one end of the cylindrical shaft, serving as theaxle, and the wheel. Also, the sealing portion seals between the wheeland the motor in a manner surrounding the coupling portion.Consequently, the coupling portion is disposed within a sealed spacesealed by the sealing portion. This allows protection of the couplingportion from disturbance, such as stones scattered by the wheel duringtravel of the electric vehicle or access to the nut by a person such asan occupant.

According to an embodiment of the present invention, the motor shaft isinserted into the hollow portion of the cylindrical shaft substantiallycoaxially with the cylindrical shaft. Thus, the structure of the shaftfor rotating the wheel has a double structure of the motor shaft and thecylindrical shaft, thereby allowing an increase in stiffness of theshaft.

Also, the wheel, the cylindrical shaft, and the motor shaft aresubstantially coaxially disposed. The motor and the reduction mechanismare each connected to the motor shall. Further, the reduction mechanismis connected to the wheel through the cylindrical shaft and the couplingportion. Consequently, a drive system of the wheel, from the motor tothe wheel through the motor shaft., the reduction mechanism, thecylindrical shaft, and the coupling portion, is disposed on the axis ofthe wheel. Thus, the drive system can be compactly disposed on the wheelwithout protruding the drive system from both sides of the wheel. Inaddition, flexibility in the space around the wheel is increased. Also,in the reduction mechanism, the torque of the wheel can be easilyincreased in accordance with the rotational drive force of the motor.

According to an embodiment of the present invention, the couplingportion is composed of: the threaded portion formed at the one end ofthe cylindrical shaft; and the nut threaded onto the threaded portion,thereby allowing easy coupling between the cylindrical shaft and thewheel.

Also, the coupling portion is provided within the sealed space betweenthe wheel and the motor which is sealed by the sealing portion. Thus,intrusion of mud, etc. from the outside can be avoided, therebyeliminating the need for forming the nut with a coarse pitch to provideresistance to thread stripping. Consequently, the nut can be formed witha fine pitch so that the tightening accuracy can be increased.

According to an embodiment of the present invention, the first bearingis inserted between the motor case and the wheel, thereby allowing afurther increase in stiffness of the drive system.

According to an embodiment of the present invention, the portion of themotor case opposite the coupling portion is tapered so as to deviatefrom the nut. Thus, the motor case (the motor in the motor case) can bebrought close to the wheel. Consequently, even if the nut comes looseduring travel of the electric vehicle, the nut can be tightened bycontact between the tapered portion and the nut, so that the motor casecan be further compactly stored on the wheel.

According to an embodiment of the present invention, the second bearingis inserted between the reduction mechanism case and the wheel, therebyallowing a still further increase in stiffness of the drive system.

According to an embodiment of the present invention, the labyrinthstructure is formed between the reduction mechanism case and the wheelin a manner surrounding the second bearing. Thus, intrusion of dust,etc. from the outside can be avoided.

According to an embodiment of the present invention, the brake isprovided in the hollow portion between the labyrinth structure and thesecond bearing, thereby enabling efficient braking of rotation of thewheel while eliminating external environmental influences.

According to an embodiment of the present invention, the third bearingis inserted between the motor case and the motor shaft. Thus, by theapplication of sealing to at least one of the first to third bearings,intrusion of dust, etc. from the outside is effectively avoided, so thatthe coupling portion or the brake can be reliably protected from thedisturbance. Also, sealing of the first to third bearings allows easyand efficient sealing between the wheel and both of the motor module andthe reduction mechanism module.

According to an embodiment of the present invention, the sealing portionis the labyrinth structure formed between the motor case and the wheelin a manner surrounding the first bearing, and/or the sealed firstbearing. Thus, intrusion of dust, etc. from the outside can be reliablyand efficiently avoided.

According to an embodiment of the present invention, the hole portion orthe bolt head is formed at the leading end of the motor shaft. Thus,rotational force is transmitted to the cylindrical shaft through thereduction mechanism by rotating the hole portion with a screw-driver ora hex wrench while fixing the nut, or rotating the bolt head with awrench. Thus, large tightening force can be generated in the couplingportion by small rotational force.

According to an embodiment of the present invention, the hole portion orthe bolt head is formed at the end of the reduction shaft toward thesecond gear. Thus, rotational force is transmitted to the cylindricalshaft by rotating the hole portion with a screw-driver or a hex wrenchwhile fixing the nut, or rotating the bolt head with a wrench. Also inthis case, large tightening force can be generated in the couplingportion by small torque.

According to an embodiment of the present invention, the sealing memberis inserted between the other end of the cylindrical shaft and the motorshaft, thereby reducing the difference between the rotational speed ofthe motor shaft and the rotational speed of the cylindrical shaftreduced by the reduction mechanism and allowing an increase indurability.

According to an embodiment of the present invention, the motor and thereduction mechanism are supported by the double-sided swing arm. Thus,the motor shaft, the cylindrical shaft, and the wheel can be supportedon both sides.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a left side view of a two-wheeled electric vehicle accordingto the present embodiment;

FIG. 2 is a right side view of the two-wheeled electric vehicle of FIG.1;

FIG. 3 is a schematic plan view of a motor module, a reduction mechanismmodule, a motor shaft, an axle, and a rear wheel which are supported bya double-sided swing arm;

FIG. 4 is a partially-exploded perspective view of a left arm of theswing arm of FIG. 3;

FIG. 5A is a side view of an arm portion of FIG. 4; and FIG. 5B is asectional view of the arm portion of FIG. 4;

FIG. 6 is an exploded perspective view of the motor module of FIG. 3;

FIG. 7 is a sectional view of the motor module, the reduction mechanismmodule, the motor shaft, the axle, and the rear wheel of FIG. 3;

FIG. 8 is a sectional view illustrating an alternative construction ofthe reduction mechanism module of FIG. 7;

FIG. 9 is a sectional view illustrating an alternative construction ofthe reduction mechanism module of FIG. 7;

FIG. 10 is a sectional view illustrating an alternative construction ofthe reduction mechanism module of FIG. 7;

FIG. 11 is a sectional view illustrating an alternative construction ofthe reduction mechanism module of FIG. 7;

FIG. 12 is a right side view of the two-wheeled electric vehicle,illustrating an alternative construction in terms of coupling betweenthe swing arm and the reduction mechanism module; and

FIG. 13 is a schematic plan view of the swing arm, the motor module, thereduction mechanism module, the motor shaft, the axle, and the rearwheel, illustrating the alternative construction of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of an electric vehicle according tothe present invention will be described in detail with reference to theaccompanying drawings.

FIG. 1 is a left side view of a two-wheeled electric vehicle (electricvehicle) 10 according to this embodiment. FIG. 2 is a right side view ofthe two-wheeled electric vehicle 10.

The two-wheeled electric vehicle 10 is a scooter type two-wheeledvehicle having a step floor 12, in which a rear wheel WR is driven byrotational drive force of a motor 16 (see FIG. 3) provided in a swingarm 14. A high-voltage (for example, 72 V) main battery 18 for supplyingelectric power to the motor 16 has a plurality of modules with aplurality of battery cells connected in series.

A head pipe 24 rotatably journaling a steering stem 22 is coupled to anupper end of a main frame 20. A pair of left and right front forks 26 land 26 r rotatably journaling a front wheel WF is mounted to thesteering stem 22. The front wheel WF can be steered by a steeringhandlebar 28 mounted to an upper portion of the steering stem 22 andhaving an accelerator grip. The steering handlebar 28 is provided with athrottle sensor 30 that detects an accelerator grip turning angle, i.e.,an accelerator opening.

A pair of left and right side frames 32 l and 32 r extending rearwardlyof a vehicle body are connected to the main frame 20. Rear frames 34 land 34 r extending upwardly and rearwardly of the vehicle body areconnected to the pair of left and right side frames 32 l and 32 r. Pivotplates 38 l and 38 r formed with a swing arm pivot 36 are mounted torear portions of the side frames 32 l and 32 r.

A front end 42 of the double-sided swing arm 14 that supports the rearwheel WR with both left and right arms 40 l and 40 r is swingablyjournaled to the swing arm pivot 36. The rear wheel WR is rotatablyjournaled through an axle 52 (see FIG. 3) to a motor case 44 (a motormodule 46 including the motor case 44) on the left side and a reductionmechanism case 48 (a reduction mechanism module 50 including thereduction mechanism case 48) on the right side, which serve as rear endsof the swing arm 14. The motor case 44 and the reduction mechanism case48 are suspended from the rear frames 34 l and 34 r by rear suspensions54 l and 54 r, respectively. Also, a taillight 56 is provided on therear frames 34 l and 34 r.

A side stand 58 is provided on the pivot plate 38 l. The side stand 58has a side-stand switch 60 that outputs a detection signal when the sidestand 58 is stored in a predetermined position.

Air introduction pipes 62 l and 62 r are connected to a front portion ofthe main battery 18. A suction fan 64 is provided on a rear portion ofthe main battery 18. The suction fan 64 allows air to be introduced intothe main battery 18 from the air introduction pipes 62 l and 62 r anddischarged rearwardly of the vehicle body. Thus, heat generated by themain battery 18 can be cooled by outside air.

A storage space 66 is provided between the pair of left and right rearframes 34 l and 34 r. A low-voltage (for example, 12 V) sub-battery 70,which is charged from the main battery 18 or from an external source, isstored in a storage space bottom 68 protruding downward from the storagespace 66. Also, the storage space 66 is provided with a PDU (Power DriveUnit) 72 that transforms direct current supplied from the main battery18 into alternating current to supply the current to the motor 16. ADC-DC down converter (hereinafter referred to as a down converter) 74 isprovided at the rear of the storage space 66. A rider's seat 76, alsoserving as a lid of the storage space 66, is provided above the storagespace 66. The rider's seat 76 is provided with a seat switch 78 thatoperates to output a seating signal when a rider sits on the seat 76. Itshould be noted that an electric power supply line 80 for supplyingalternating current to the motor 16 from the PDU 72 is provided betweenthe storage space 66 and the motor 16.

A bracket 82 is coupled to a front portion of the head pipe 24. Aheadlight 84 is mounted to a front end of the bracket 82. Also, a meterunit 86 for showing the vehicle speed or the like is provided in thevicinity of the steering handlebar 28.

Next, a construction around the rear wheel WR of the two-wheeledelectric vehicle 10 will be described in relation to the double-sidedswing arm 14 with reference to FIGS. 1 to 7.

The swing arm 14 is, as described above, the double-sided swing arm thatsupports the rear wheel WR with both the left and right arms 40 l and 40r.

More specifically, the front end 42 (a fifth arm portion and an eightharm portion) of the swing arm 14 is composed of a hollow cylinderportion 42 a allowing insertion of the swing arm pivot 36; arm portions42 l and 42 r respectively extending rearward from both the left andright sides of the cylinder portion 42 a; and a connection portion 42 bconnecting between both the left and right arm portions 42 l and 42 r.

The left arm 40 l extends from the front end 42 to the left side (oneside) of a wheel 90 constituting the rear wheel WR serving as a wheelassembly. In other words, the arm 40 l is composed of theabove-described arm portion 42 l; an arm portion 92 (a connectionportion, a third arm portion) coupled to a rear portion of the armportion 42 l in a vehicle width direction; an arm portion 94 (aconnection portion, a fourth arm portion) coupled to the arm portion 92in the vehicle width direction; and the motor case 44 coupled to a rearportion of the arm portion 92 in the vehicle width direction.

Also, the motor case 44 is composed of a storage portion 44 a (a firstarm portion) that is formed with a recessed portion allowing thereception of the motor 16; and a lid portion 44 b (a second arm portion)that covers the storage portion 44 a in the vehicle width direction withthe motor 16 received in the recessed portion of the storage portion 44a, thereby closing the motor 16 in cooperation with the storage portion44 a. Therefore, the motor 16 is disposed in the storage portion 44 a,and the storage portion 44 a is covered with the lid portion 44 b toconstitute the motor case 44, so that the motor module 46 including themotor 16 and the motor case 44 is constituted.

The arm portions 42 l, 92, 94, the storage portion 44 a, and the lidportion 44 b are coupled to one another in the vehicle width direction(the left-right direction in FIG. 3) of the two-wheeled electric vehicle10.

More specifically, plate-like portions 96 a and 96 b extend verticallyfrom a rear end of the arm portion 42 l. Also, the arm portion 92 is aplate-like member, of generally substantially C-shaped cross-section,formed in such a manner that a front end thereof covers a rear end ofthe arm portion 42 l and the left side of the plate-like portions 96 aand 96 b. On the right side of the arm portion 92, plate-like portions98 a and 98 b extend vertically. Furthermore, the arm portion 94 is aplate-like member, of substantially C-shaped cross section, opposed tothe arm portion 92 of substantially C-shaped cross section. On the leftside of the arm portion 94, plate-like portions 100 a and 100 b extendvertically opposite to the plate-like portions 98 a and 98 b,respectively. Moreover, on a front end of the storage portion 44 a, armportions 102 a and 102 b extend forwardly toward the plate-like portions98 a and 98 b of the arm portion 92.

Therefore, with front ends of the plate-like portions 98 a and 98 bsuperposed on rear ends of the plate-like portions 96 a and 96 b, bolts110 a and 110 b are respectively inserted into bores 108 a and 108 bformed in the front ends of the plate-like portions 98 a and 98 b, andthreaded into nuts 112 a and 112 b welded and fixed to the rear ends ofthe plate-like portions 96 a and 96 b in the vehicle width direction,thereby allowing coupling between the arm portion 42 l and the armportion 92 in the vehicle width direction.

Also, with central portions of the plate-like portions 98 a and 98 bsuperposed on the plate-like portions 100 a and 100 b, bolts 118 a to118 c are inserted into a total of three bores 114 a to 114 c (two bores114 a and 114 b of the plate-like portion 98 a and a single bore 114 cof the plate-like portion 98 b) formed in the central portions of theplate-like portions 98 a and 98 b, and three bores 116 a to 116 c formedopposite to the three bores 114 a to 114 c, respectively, in theplate-like portions 100 a and 100 b, and threaded into weld nuts 120 ato 120 c fixed to the plate-like portions 100 a and 100 b, therebyallowing coupling between the arm portion 92 and the arm portion 94 inthe vehicle width direction.

Furthermore, with rear ends of the plate-like portions 98 a and 98 bsuperposed on leading ends of the arm portions 102 a and 102 b, bolts126 a and 126 b are inserted into bores 122 a and 122 b formed in therear ends of the plate-like portions 98 a and 98 b, respectively, andthreaded into threaded bores 124 a and 124 b formed in the leading endsof the arm portions 102 a and 102 b, respectively, thereby allowingcoupling between the arm portion 92 and the arm portions 102 a and 102 b(the storage portion 44 a including the arm portions 102 a and 102 b) inthe vehicle width direction.

Moreover, four threaded holes 128 a to 128 d are circumferentiallyformed in the storage portion 44 a that is substantially circular inside view. Also, bores 130 a to 130 d are formed opposite to thethreaded holes 128 a to 128 d, respectively, in the substantiallydisk-shaped lid portion 44 b (see FIG. 6). Therefore, with the bores 130a to 130 d aligned with the threaded holes 128 a to 128 d, bolts 132 ato 132 d are inserted into the bores 130 a to 130 d and threaded intothe threaded holes 128 a to 128 d, respectively, thereby allowingcoupling between the lid portion 44 b and the storage portion 44 a inthe vehicle width direction.

It should be noted that the bottom of the storage portion 44 a ismachined flat, and the bottom of the lid portion 44 b is also machinedflat so as to correspond to the bottom of the storage portion 44 a.Also, an arm portion 102 c extends rearward on a rear portion of thestorage portion 44 a. The rear suspension 54 l is connected to a bore124 c formed in a leading end portion of the arm portion 102 c.

An expanded portion 134 expanding forward is formed at a portion inbetween the arm portions 102 a and 102 b of the storage portion 44 a.Also, an expanded portion 136 expanding forward, which corresponds tothe expanded portion 134, is formed on the lid portion 44 b.

The motor 16 is an inner rotor type three-phase motor that is composedof a motor shaft 16 a substantially coaxially inserted into the hollowcylindrical axle 52 (see FIG. 7); a rotor 16 b substantially coaxiallyconnected to the motor shaft 16 a; and an annular stator 16 csurrounding the rotor 16 b. The motor 16 is stored in the motor case 44by fixing the stator 16 c to the recessed portion of the storage portion44 a and disposing, within the stator 16 c, the rotor 16 b with themotor shaft 16 a passing therethrough (see FIGS. 3, 5, and 6). In thiscase, bus bar connecting terminals 138 a to 138 c (connecting portions),facing forward, are provided at a portion of the motor 16 toward theexpanded portions 134 and 136, in such a manner so as to be sandwichedbetween the expanded portions 134 and 136.

As described above, the arm portions 92 and 94 of substantially C-shapedcross section are coupled to each other in the vehicle width direction,thereby forming a longitudinally-extending hollow portion 140 at theC-shaped portions by coupling between the respective arm portions 92, 94(see FIGS. 5A and 5B). Also, the electric power supply line 80 runs fromthe PDU 72 (see FIGS. 1 to 3). The electric power supply line 80 extendsdownwardly from the rear of the storage space 66 storing the PDU 72 andpasses the side of the arm portion 42 l of the swing arm 14 to enter thehollow portion 140 through between leading ends 142 a and 142 b of thearm portion 94 which is upwardly curved in an arc, and reach theconnecting terminals 138 a to 138 c.

In this case, the electric power supply line 80 is composed of bus bars80 a to 80 c as a three-phase line. The bus bars 80 a to 80 c, betweenthe storage space 66 and the leading ends 142 a and 142 b of the armportion 94, are externally electrically insulated by an insulatingsheath 144. Within the hollow portion 140, a supporting member 150 ofsubstantially C-shaped cross section made of an electrical insulatingmaterial is fixed to the arm portion 94 by threaded engagement of ascrew 146 with a nut 148. Thus, the bus bars 80 a to 80 c are supportedby the supporting member 150 in such a way so as to prevent contact withthe arm portions 92 and 94. Also, bores 154 a to 154 c allowinginsertion of screws 152 a to 152 c are formed in leading ends of the busbars 80 a to 80 c toward the motor 16.

Therefore, the screws 152 a to 152 c are inserted into the bores 154 ato 154 c and threaded into threaded bores 156 a to 156 c formed in theconnecting terminals 138 a to 138 c, respectively, thereby allowingfixation (connection) of the bus bars 80 a to 80 c to the connectingterminals 138 a to 138 c, respectively. Consequently, the rotor 16 b andthe motor shaft 16 a can be driven to rotate by supplying three-phasealternating current to the motor 16 from the PDU 72 through the bus bars80 a to 80 c and the connecting terminals 138 a to 138 c.

On the other hand, the right arm 40 r extends from the front end 42 tothe right side (the other side) of the wheel 90 (see FIGS. 2 and 3). Inother words, the arm 40 r is composed of the above-described arm portion42 r, and the reduction mechanism case 48 coupled to a rear portion ofthe arm portion 42 r.

Also, the reduction mechanism case 48 is composed of a first storageportion 48 a that is provided on the right side of the wheel 90 andformed with a recessed portion allowing the reception of a reductionmechanism 160; a second storage portion 48 b that is coupled to thefirst storage portion 48 a in the vehicle width direction in such amanner as to surround a side portion of the reduction mechanism 160; anda lid portion 48 c (a seventh arm portion) that covers the secondstorage portion 48 b in the vehicle width direction with the reductionmechanism 160 disposed in the first and second storage portions 48 a and48 b (sixth arm portions), thereby closing the reduction mechanism 160in cooperation with the first and second storage portions 48 a and 48 b.Therefore, the reduction mechanism 160 is disposed in the first andsecond storage portions 48 a and 48 b, and the second storage portion 48b is covered with the lid portion 48 c to constitute the reductionmechanism case 48, so that the reduction mechanism module 50 includingthe reduction mechanism 160 and the reduction mechanism case 48 isformed.

In the arm 40 r, the arm portion 42 r, the first storage portion 48 a,the second storage portion 48 b, and the lid portion 48 c are coupled toone another in the vehicle width direction.

More specifically, a plate-like portion 162 that is V-shaped in sideview extends rearward from a rear end of the arm portion 42 r. Also, armportions 164 a and 164 b extend toward the plate-like portion 162 fromthe first storage portion 48 a. Therefore, bolts 166 a and 166 b areinserted into two bores, not shown, of the plate-like portion 162 andthreaded into threaded holes, not shown, of the arm portions 164 a and164 b, respectively, thereby allowing coupling between the plate-likeportion 162 (of the arm portion 42 r) and the arm portions 164 a and 164b (of the first storage portion 48 a) in the vehicle width direction.Also, the first storage portion 48 a, the second storage portion 48 b,and the lid portion 48 c can be sequentially coupled in the vehiclewidth direction by using bolts not shown or the like.

It should be noted that an arm portion 164 c extends rearward on a rearportion of the first storage portion 48 a. The rear suspension 54 r isconnected to a bore 168 formed in a leading end portion of the armportion 164 c. The rear suspension 54 r is connected to the arm portion164 c forwardly with respect to the rear suspension 54 l in a plan viewof FIG. 3.

The reduction mechanism 160 is connected to the motor shaft 16 aextending to the right side of the wheel 90. Also, the reductionmechanism 160 rotates the axle 52 at a rotational speed lower than thatof the motor shaft 16 a rotated by driving of the motor 16, therebyrotating the rear wheel WR including the wheel 90 connected to the axle52.

Next, a more concrete explanation of the wheel 90, and the motor module46 and the reduction mechanism module 50 respectively disposed on theleft and right sides of the wheel 90, will be made with reference to asectional view of FIG. 7.

The hollow cylindrical axle 52 passes substantially coaxially throughthe wheel 90 constituting the rear wheel WR serving as the wheelassembly. In this case, the outer and inner diameters of a left-handportion of the axle 52 passing through the wheel 90 are smaller thanthose of a right-hand portion thereof connected to the reductionmechanism 160. Consequently, the axle 52 is formed as a cylindricalshaft having a shoulder. Also, a portion on an outer peripheral surfaceof the axle 52 which passes through the wheel 90 is subjected to splineprocessing to engage spline grooves of the wheel 90 (see FIGS. 3 and 7).Further, a thread groove (threaded portion), not shown, is formed at aleft end (one end) of the axle 52 protruding slightly from the wheel 90.Therefore, with a washer 170 attached to the axle 52, a nut 172 isthreaded onto the thread groove, thereby allowing coupling between thewheel 90 and the axle 52. It should be noted that the thread groove, thewasher 170, and the nut 172 constitute a coupling portion 192 forcoupling the wheel 90 and the axle 52.

The motor shaft 16 a is substantially coaxially inserted into the axle52 so as to extend on both sides from both ends of the axle 52. In thiscase, the motor shaft 16 a is formed as a columnar shaft having ashoulder so as to conform to the shape of a hollow portion of the axle52.

The motor shaft 16 a passes through the rotor 16 b of the motor 16. Athread groove, not shown, is formed at a left end of the motor shaft 16a protruding leftward from the rotor 16 b. With a washer 174 attached tothe motor shaft 16 a, a nut 176 is threaded onto the thread groove,thereby allowing coupling between the motor shaft 16 a and the rotor 16b. Also, a removable cap 180 is disposed at a central portion of the lidportion 44 b, opposite to the left end of the motor shaft 16 a.

Also, on the side of the storage portion 44 a toward the wheel 90, thereare provided annular protruding portions 182 and 184 protruding towardthe wheel 90 in such a manner as to surround the motor shaft 16 a. Onthe side of the wheel 90 toward the storage portion 44 a, there areprovided, between the above-described protruding portions 182 and 184,annular protruding portions 186 and 188 protruding toward the storageportion 44 a in such a manner so as to surround the motor shaft 16 a.

In this case, between the protruding portion 184 of the storage portion44 a and the protruding portion 188 of the wheel 90 is a labyrinthstructure 190.

Also, a bearing 194 (a first bearing) is disposed between the protrudingportions 182 and 186 provided inwardly with respect to the protrudingportions 184 and 188. The motor case 44 (the motor module 46) issupported in a relatively rotatable manner with respect to the wheel 90by the bearing 194. Consequently, the labyrinth structure 190 preventsstones, etc. scattered by the rear wheel WR during operation of thetwo-wheeled electric vehicle 10 from being directly splashed onto thebearing 194. It should be noted that a seal bearing is employed as thebearing 194 to seal a space toward the motor shaft 16 a.

Furthermore, a portion of the protruding portion 182 opposite the nut172 is formed as a tapered portion 195 that is tapered so as to deviatefrom the nut 172 (so as to spread toward the nut 172).

Moreover, a portion of the motor shaft 16 a which is in between therotor 16 b and the axle 52 is formed with a shoulder. A collar 196 isattached to the shoulder. Also, a bearing 198 is inserted between therotor 16 b, the collar 196, and the protruding portion 182. On the otherhand, a bearing 200 is attached between the side of the rotor 16 btoward the cap 180, and the lid portion 44 b. The motor case 44 issupported in a relatively rotatable manner with respect to the motorshaft 16 a and the rotor 16 b by the bearings 198 and 200. It should benoted that the bearings 198 and 200 are also seal bearings.

On the other hand, the right end of the motor shall is supported throughbearings 210 and 212 by the second storage portion 48 b and the lidportion 48 c.

The reduction mechanism 160 is composed of a gear portion 216 (a firstgear) formed at a portion of the motor shaft 16 a which is in betweenthe bearings 210 and 212; a reduction shaft 218 disposed forwardly withrespect to the motor shaft 16 a and the axle 52, and substantiallyparallel to the motor shaft 16 a and the axle 52; a gear 220 (a secondgear) disposed on the side of the reduction shaft 218 toward the lidportion 48 c, and engaging with the gear portion 216; a gear portion 222(a third gear) formed on the side of the reduction shaft 218 toward thewheel 90; and a gear 224 (a fourth gear) disposed on a right end of theaxle 52 and engaging with the gear portion 222.

Also, within the reduction mechanism case 48, both ends of the reductionshaft 218 are supported through bearings 226 and 228 by the firststorage portion 48 a and the lid portion 48 c. The gear 224 is fixedthrough a bearing 230 to the right end of the axle 52 and the secondstorage portion 48 b. Further, the reduction mechanism 160 is injectedwith oil so as to prevent seizing up of the gear portions 216 and 222and the gears 220 and 224. Therefore, oil seals 232 and 234 are insertedbetween the right end of the axle 52 and the motor shaft 16 a, andbetween the side of the first storage portion 48 a toward the wheel 90,and the axle 52, respectively.

An annular recessed portion 240 is formed at a portion of the wheel 90opposite the first storage portion 48 a. Also, an annular recessedportion 242 is formed opposite to the annular recessed portion 240 onthe side of the first storage portion 48 a toward the wheel 90. Thus,annular protruding portions 244 and 246 protruding toward the firststorage portion 48 a in a manner surrounding the axle 52 are formed on aright side surface of the wheel 90. Also, annular protruding portions248 and 250 protruding toward the wheel 90 in a manner surrounding theaxle 52 are formed on the side of the first storage portion 48 a towardthe wheel 90.

In this case, a labyrinth structure 252 is formed between the protrudingportion 246 of the wheel 90 and the protruding portion 250 of the firststorage portion 48 a. The labyrinth structure 252 seals a space on theinside of the protruding portions 246 and 250 formed by the annularrecessed portions 240 and 242.

Also, a bearing 254 (a second bearing) serving as a seal bearing isprovided between the axle 52 and each of the protruding portions 244 and248 formed inwardly with respect to the protruding portions 246 and 250,respectively. The reduction mechanism case 48 (the reduction mechanismmodule 50) is supported in a relatively rotatable manner with respect tothe wheel 90 by the bearing 254.

Furthermore, a drum brake 260 is provided toward the annular recessedportion 240 in the sealed space formed by the labyrinth structure 252,in such a manner as to surround the axle 52.

The drum brake 260 is a well-known drum brake mechanism, and composed ofa drum 262 attached to the wheel 90, a leading shoe 266 mounted with alining 264, and a trailing shoe 270 mounted with a lining 268. In thiscase, a spring member, not shown, is inserted between the leading shoe266 and the trailing shoe 270. When the leading shoe 266 and thetrailing shoe 270 are longitudinally moved away from each other againstthe tension of the spring member by a hydraulic cylinder or the like,the lining 264 of the leading shoe 266 and the lining 268 of thetrailing shoe 270 press against the drum 262, thereby enabling brakingof rotation of the wheel 90 attached with the drum 262.

It should be noted that in this embodiment, a disc brake may of coursebe used in place of the drum brake 260 as long as it can brake therotation of the wheel 90.

The two-wheeled electric vehicle 10 according to this embodiment isconstructed as above. Next, mounting/removal of the rear wheel WR, themotor module 46, and the reduction mechanism module 50 to/from thetwo-wheeled electric vehicle 10, and replacement (both of mounting andremoval) thereof will be described with reference to FIGS. 1 to 7.

First of all, mounting of the rear wheel WR, the motor module 46, andthe reduction mechanism module 50 to the two-wheeled electric vehicle 10will be described.

Firstly, the reduction mechanism module 50 with the motor shaft 16 a andthe axle 52 mounted is mounted to the two-wheeled electric vehicle 10.In this case, an operator couples the plate-like portion 162 and the armportions 164 a and 164 b in the vehicle width direction by inserting thebolts 166 a and 166 b into the two holes of the plate-like portion 162extending from the arm portion 42 r of the swing arm 14, and threadingthe bolts 166 a and 166 b into the threaded holes, not shown, of the armportions 164 a and 164 b provided on the reduction mechanism module 50.Also, the operator attaches the drum brake 260 to the axle 52 and thenconnects the rear suspension 54 r to the bore 168 of the arm portion 164c.

Next, the rear wheel WR serving as the wheel assembly is mounted to theaxle 52.

In this case, the operator mounts the rear wheel WR to the axle 52 insuch a manner that the spline structure formed on the left end of theaxle 52 fits the spline grooves formed in the wheel 90. It should benoted that the bearing 194 is also previously attached to the wheel 90.

And then the operator tightens the nut 172 with a wrench with the rearwheel WR fixed.

Next, the operator mounts the motor module 46 to the motor shaft 16 a.

In this case, the operator attaches the collar 196 to the motor shaft 16a, and then mounts the motor module 46 to the motor shaft 16 a in such amanner that the motor shaft 16 a is inserted into the hollow portion(the central axis) of the rotor 16 b. Then after the cap 180 is removedfrom the lid portion 44 b and the washer 174 is attached to the motorshaft 16 a, the nut 176 is threaded onto the thread groove of the motorshaft 16 a so as to fix the motor shaft 16 a and the rotor 16 b. Afterfixing the motor shaft 16 a and the rotor 16 b, the operator mounts thecap 180 to the lid portion 44 b and then mounts the rear suspension 54 lto the bore 124 c of the arm portion 102 c.

Next, the arm portions 42 l, 92, and 94, and the motor case 44 arecoupled in the vehicle width direction.

In this case, firstly, the bus bars 80 a to 80 c and the connectingterminals 138 a to 138 c are connected to each other. That is, thescrews 152 a to 152 c are inserted into the bores 154 a to 154 c andthreaded into the threaded bores 156 a to 156 c of the connectingterminals 138 a to 138 c, respectively, thereby connecting the bus bars80 a to 80 c and the connecting terminals 138 a to 138 c.

Next, the arm portion 92 and the arm portion 42 l are coupled to eachother in the vehicle width direction. Also, the arm portion 92 and thearm portions 102 a and 102 b are coupled to each other in the vehiclewidth direction.

In this case, the bolts 126 a and 126 b are inserted into the bores 122a and 122 b of the plate-like portions 98 a and 98 b of the arm portion92 and threaded into the threaded bores 124 a and 124 b of the armportions 102 a and 102 b, thereby allowing coupling between the armportion 92 and the arm portions 102 a and 102 b in the vehicle widthdirection. Also, the bolts 110 a and 110 b are inserted into the bores108 a and 108 b of the plate-like portions 98 a and 98 b and threadedinto the nuts 112 a and 112 b, respectively, thereby allowing couplingbetween the arm portion 42 l and the arm portion 92 in the vehicle widthdirection.

Furthermore, with the bus bars 80 a to 80 c supported by the supportingmember 150, the bolts 118 a to 118 c are inserted into the bores 114 ato 114 c and the bores 116 a to 116 c and threaded into the weld nuts120 a to 120 c, respectively, thereby allowing coupling between the armportion 92 and the arm portion 94 in the vehicle width direction. Also,the bus bars 80 a to 80 c can be supported within the hollow portion 140without making contact with inner walls of the arm portions 92 and 94.

In the above-described manner, the rear wheel WR, the motor module 46,and the reduction mechanism module 50 can be mounted to the two-wheeledelectric vehicle 10.

Next, as to removal of the rear wheel WR, the motor module 46, and thereduction mechanism module 50 from the two-wheeled electric vehicle 10,it can be performed by reversing the above-described mounting procedure.

In this embodiment, the left arm 40 l of the swing arm 14 can beseparated into the arm portions 42 l, 92, 94, and the motor case 44.Also, in side view, the outer periphery or outside of the rear wheel WRis a separation point (a separation point between the arm portion 42 land the arm portion 92). Consequently, the motor module 46 and the rearwheel WR can be removed in one direction by releasing the coupling inthe vehicle width direction of the arm portions 42 l, 92, and 94. Itshould be noted that the concept of the outer periphery of the rearwheel WR is not limited to the outer periphery itself but includes thevicinity of the outer periphery (portions of a diameter slightly smalleror larger than the outside diameter of the rear wheel WR).

Also, replacement of the rear wheel WR, the motor module 46, and thereduction mechanism module 50 can be easily performed by adopting theabove-described mounting and removal procedures.

As described above, in the two-wheeled electric vehicle 10 according tothis embodiment, the motor 16 is disposed on the left side (one side) ofthe wheel 90, while the reduction mechanism 160 is disposed on the rightside (the other side) of the wheel 90. In this case, the motor shaft 16a passes through the hollow portion of the axle 52 connected to thewheel 90 to extend from both ends of the axle 52. Also, the rotor 16 bof the motor 16 is connected to the left end of the motor shaft 16 a,while the reduction mechanism 160 is connected to the right end of themotor shaft. In this manner, the motor 16 is disposed on one side of thewheel 90, and on the other side of the wheel 90 is the reductionmechanism 160, thereby easily achieving a weight balance. In addition,the motor shaft 16 a is inserted into the hollow portion of the axle 52substantially coaxially with the axle 52. Thus, the shaft for rotatingthe wheel 90 has a double structure of the motor shaft 16 a and the axle52, thereby allowing an increase in stiffness of the shaft.

Also, the wheel 90, the axle 52, and the motor shaft 16 a aresubstantially coaxially disposed. The motor 16 and the reductionmechanism 160 are each connected to the motor shaft 16 a. Further, thereduction mechanism 160 is connected to the wheel 90 through the axle52. Consequently, a drive system of the wheel 90, from the motor 16 tothe wheel 90 through the motor shaft 16 a, the reduction mechanism 160,and the axle 52, is disposed on the axis of the wheel 90. Thus, thedrive system can be compactly disposed on the wheel 90 withoutprotruding the drive system to the left or right side of the wheel 90.In addition, flexibility in the space around the wheel 90 is increased.Also, in the reduction mechanism 160, the torque of the wheel 90 can beeasily increased in accordance with the rotational drive force of themotor 16.

In this manner, in this embodiment, the periphery of the wheel 90 isconstructed as above, thereby allowing the realization of thetwo-wheeled electric vehicle 10 in which weight balance is easilyachieved and the drive system, such as the motor 16, can be compactlydisposed on the wheel 90.

Also, by achieving weight balance as described above, it is possible tosupport the wheel 90, the axle 52, and the motor shaft 16 a on bothsides through the motor module 46 including the motor 16 and thereduction mechanism module 50 including the reduction mechanism 160,without unnecessary reinforcement (increase in stiffness) or increase inweight of the double-sided swing arm 14.

Furthermore, the motor 16 is modularized as the motor module 46, and thereduction mechanism 160 is modularized as the reduction mechanism module50, thereby facilitating the mounting/removal of the motor module 46(the motor 16) and the reduction mechanism module 50 (the reductionmechanism 160) to/from the wheel 90 or the replacement thereof, andallowing prevention of dust contamination with the adhesion ordeposition of foreign particles, such as dirt and dust, to the motor 16or the reduction mechanism 160.

Moreover, the motor module 46 is relatively rotatably mounted to thewheel 90 through the bearing 198, and the reduction mechanism module 50is relatively rotatably mounted to the wheel 90 through the bearing 254.Thus, mounting/removal of the motor module 46 and the reductionmechanism module 50 to/from the wheel 90 or replacement thereof can befurther facilitated.

Also, the rear suspensions 54 l and 54 r are mounted to the motor module46 and the reduction mechanism module 50, respectively. Thus, the shockdue to uneven roads or the like is effectively absorbed, therebyallowing an improvement in the occupant ride quality of the two-wheeledelectric vehicle 10.

Furthermore, the left end of the motor shaft 16 a is fixed to the rotor16 b, and the right end of the motor shaft is supported by the bearings210 and 212 provided on the reduction mechanism 160, thereby allowing animprovement in the operational efficiency of mounting/removal of therotor 16 b and the reduction mechanism 160 to/from the motor shaft 16 aor replacement thereof.

Moreover, the reduction shaft 218, the gear 220, and the gear portion222, which are major portions of the reduction mechanism 160, areprovided in front of the axle 52 and the motor shaft 16 a. Consequently,the center of gravity of the reduction mechanism 160 is located forwardwith respect to the axle 52 and the motor shaft 16 a, so that thetwo-wheeled electric vehicle 10 having an excellent weight balance canbe realized.

Also, the drum brake 260 is disposed on the right side of the wheel 90in a state of passing through the axle 52 and the motor shaft 16 a. Thisallows reliable braking of rotation of the wheel 90 while achievingweight balance.

Also, in the two-wheeled electric vehicle 10 according to thisembodiment, the left side (the left arm 40 l) of the swing arm 14 withrespect to the wheel 90 is composed of the plurality of arm portions 42l, 92, and 94 and the motor case 44 which can be separated. Thus, thewheel 90 and the motor 16 can be removed or mounted in one directionjust by removing the arm portions 92 and 94 from the two-wheeledelectric vehicle 10, on the left side of the wheel 90. In other words,removal or mounting of the rear wheel WR (the wheel assembly) and themotor case 44 can be easily performed from the left side of the wheel 90by removing the arm portions 92 and 94 from the two-wheeled electricvehicle 10. Thus, the operational efficiency of mounting and removal ofthe wheel 90 and the motor 16 can be improved. Further, since the motorcase 44 is one element of the left arm 40 l, it is possible to suppressan increase in the number of components.

In this manner, in this embodiment, the periphery of the wheel 90 isconstructed as above, thereby allowing the realization of thetwo-wheeled electric vehicle 10 in which weight balance is easilyachieved and the operational efficiency of mounting, removal, andreplacement of the wheel 90 and the motor 16 can be improved.

Furthermore, the electric power supply line 80 is provided within thehollow portion 140 of the arm portions 92 and 94 connected to the motorcase 44, thereby allowing proper protection of the electric power supplyline 80 and enhancing the appearance in the portion of the two-wheeledelectric vehicle 10 where the swing arm 14 is located. Also, even if thearm portions 92 and 94 are each made of a metal material, the supportingmember 150 prevents contact between the inner walls of the arm portions92 and 94 and the electric power supply line 80. Thus, shorts in theelectric power supply line 80 can be reliably prevented.

Also, the connecting terminals 138 a to 138 c provided on the motor 16and the bus bars 80 a to 80 c composing the electric power supply line80 are connected to each other in front of the motor case 44. Thus, aconnecting region between the motor 16 and the electric power supplyline 80 can be protected. In this manner, the connecting terminals 138 ato 138 c serve as portions for fixing the bus bars 80 a to 80 c, therebyfacilitating mounting of the bus bars 80 a to 80 c to the connectingterminals 138 a to 138 c.

The arm portions 42 l, 92, and 94 and the motor case 44 are coupled toone another in the vehicle width direction. Thus, an operator, whilebeing on the left of the two-wheeled electric vehicle 10, can performremoval/mounting or replacement of the wheel 90 and the motor 16,thereby allowing an improvement in operational efficiency while reducingthe operator's work burdens. Also, the arm portions 42 l, 92, and 94 andthe motor case 44 are coupled to one another in the vehicle widthdirection. Thus, it is only necessary to remove only the element of anoperation object, so that the operational efficiency can be furtherimproved. Also, the arm portions 92 and 94 are coupled to each other inthe vehicle width direction, thereby allowing reliable formation of thehollow portion 140 for insertion of the electric power supply line 80.

Furthermore, the arm portions 42 l, 92, and 94 and the motor case 44 arecoupled to one another in the vehicle width direction by using theplurality of bolts 110 a, 110 b, 118 a to 118 c, 126 a, 126 b, 132 a to132 d, the nuts 112 a and 112 b, and the weld nuts 120 a to 120 c. Thus,the operator can further efficiently perform the mounting/removal orreplacement operation.

The right side (the right arm 40 r) of the swing arm 14 with respect tothe wheel 90 is also composed of the arm portion 42 r and the reductionmechanism case 48 which can be separated. Therefore, removal/mounting ofthe reduction mechanism 160 from/to the two-wheeled electric vehicle 10or replacement thereof can be performed on the right side of the wheel90. Also in this case, the operational efficiency of mounting, removal,and replacement of the reduction mechanism 160 can be improved.

Also, the reduction mechanism case 48 is designed to serve as an elementof the arm 40 r, thereby allowing suppression of an increase in thenumber of components. Further, since the arm portion 42 r and thereduction mechanism case 48 are coupled in the vehicle width directionby the bolts 166 a and 166 b, it is only necessary to remove only thereduction mechanism case 48, so that the operational efficiency can beimproved.

Moreover, the bottom of the motor case 44 is formed substantially flatThus, contact of the lower surface of the motor case 44 with the groundcan be suppressed.

Furthermore, in the two-wheeled electric vehicle 10 according to thisembodiment, as described above, the motor 16 is connected to the leftend of the motor shaft 16 a which is one end of the wheel 90, and on theother side thereof, the reduction mechanism 160 is connected to theright end of the motor shaft. Thus, weight balance is easily achieved.In addition, between the wheel 90 and the motor case 44, the left end ofthe axle 52 and the wheel 90 are coupled to each other by the couplingportion 192. Also, the labyrinth structure 190 seals the space inbetween the wheel 90 and the motor case 44 in a manner surrounding thecoupling portion 192. Consequently, the coupling portion 192 is disposedin the sealed space sealed by the labyrinth structure 190. Thus, thecoupling portion 192 can be protected from disturbance such as stonesscattered by the rear wheel WR during travel of the two-wheeled electricvehicle 10 or access to the nut 172 by a person such as an occupant.Also, intrusion of mud, etc. from the outside can be avoided, therebyeliminating the need for forming the nut 172 with a coarse pitch toprovide resistance to thread stripping. Therefore, the nut 172 can beformed with a fine pitch so that the tightening accuracy can beincreased.

Also, the coupling portion 192 is composed of the threaded groove formedin the outer peripheral surface of the axle 52, the washer 170, and thenut 172 threaded onto the threaded groove. Thus, coupling between theaxle 52 and the wheel 90 can be easily performed.

Also, the bearing 194 is inserted between the motor case 44 and thewheel 90, thereby allowing a further increase in stiffness of the drivesystem.

The portion (the tapered portion 195) of the motor case 44 opposite thecoupling portion 192 is tapered so as to deviate from the nut 172. Thus,the motor case 44 (the motor 16 in the motor case 44) can be broughtclose to the wheel 90, so that the motor case 44 can be furthercompactly stored in the wheel 90.

Also, in the case of the nut 172 of the right-hand thread type, even ifthe nut 172 comes loose during the operation of the two-wheeled electricvehicle 10, the contact between the tapered portion and the nut 172allows the nut 172 to be automatically tightened by the operation of thetwo-wheeled electric vehicle 10 because the rear wheel WR rotates in adirection to tighten the nut 172.

Also, the bearing 254 is inserted between the reduction mechanism case48 and the wheel 90, thereby allowing a still further increase instiffness of the drive system.

Further, the labyrinth structure 252 is formed between the reductionmechanism case 48 and the wheel 90 in a manner surrounding the bearing254. Thus, intrusion of dust, etc. from the outside can be avoided.Also, the drum brake 260 is provided in the hollow portion between thelabyrinth structure 252 and the bearing 254, thereby enabling efficientbraking of rotation of the wheel 90 while eliminating externalenvironmental influences.

Also, if the bearings 198 and 200 are inserted between the motor case 44and the motor shaft 16 a and all bearings 194, 198, 200, and 254 areseal bearings, intrusion of dust, etc. from the outside is effectivelyavoided, thereby allowing reliable protection of the coupling portion192 or the drum brake 260 from disturbance, and easy and efficientsealing between the wheel 90 and each of the motor module 46 and thereduction mechanism module 50.

Also, the oil seal 232 is inserted between the right end of the axle 52and the motor shaft 16 a, thereby reducing the difference between therotational speed of the motor shaft 16 a and the rotational speed of theaxle 52 reduced by the reduction mechanism 160 and allowing an increasein durability.

Next, modifications of this embodiment will be described with referenceto FIGS. 8 to 13.

FIG. 8 illustrates a case where a hole portion 214 allowing insertion ofa screw-driver or a hex wrench is formed in a right end of the motorshaft, and a cap 280 is attached to a portion of the lid portion 48 copposite the hole portion 214.

In this modification, at the time of tightening the nut 172 by anoperator, the operator removes the cap 280 to insert the screw-driver orthe hex wrench into the hole portion 214. On the other hand, theoperator fixes the nut 172 with a wrench, and in this state, rotates themotor shaft 16 a by using the screw-driver or the hex wrench. Then smallrotational force of the motor shaft 16 a generated by the screw-driveror the hex wrench is transmitted to the axle 52 through the gear portion216, the gear 220, the reduction shaft 218, the gear portion 222, andthe gear 224, thereby generating large tightening force in the couplingportion 192. Consequently, the nut 172 can be easily tightened againstthe wheel 90 with the large tightening force.

In this manner, in the modification of FIG. 8, the hole portion 214 isformed in the right end of the motor shaft. Thus, rotational force istransmitted to the axle 52 through the reduction mechanism 160 byrotating the hole portion 214 with a screw-driver or a hex wrench whilefixing the nut 172. Consequently, large tightening force can begenerated in the coupling portion 192 by small rotational force.

FIG. 9 illustrates a case where the cap 280 is attached to the lidportion 48 c, while a bolt head 282 is provided on a right end of themotor shaft. Also in this case, rotational force is transmitted to theaxle 52 through the reduction mechanism 160 by fixing the nut 172 withone wrench and, with the cap 280 removed, rotating the bolt head 282with the other wrench. Thus, large tightening force can be generated inthe coupling portion 192 by small rotational force. Consequently, thenut 172 can be easily tightened against the wheel 90 with the largetightening force.

FIG. 10 illustrates a case where a cap 284 is attached to the lidportion 48 c, while a hole portion 286 allowing insertion of ascrew-driver or a hex wrench is provided at a right end of the reductionshaft 218. Also in this case, a large tightening force, which, althoughnot as large as those of the structures of FIGS. 8 and 9, is to someextent larger relative to small rotational force generated in the holeportion 286, can be generated in the coupling portion 192 by fixing thenut 172 with a wrench, and, with the cap 284 removed, inserting ascrew-driver or a hex wrench into the hole portion 286 and rotating thereduction shaft 218. Consequently, the nut 172 can be tightened againstthe wheel 90.

FIG. 11 illustrates a case where the cap 284 is attached to the lidportion 48 c, while a bolt head 288 is provided on a right end of thereduction shaft 218. Also in this case, a large tightening force, whichis to some extent larger relative to small rotational force generated inthe bolt head 288, can be generated in the coupling portion 192, in thesame manner as the case of FIG. 10, by fixing the nut 172 with onewrench, and, with the cap 284 removed, rotating the bolt head 288 usingthe other wrench. Consequently, the nut 172 can be tightened against thewheel 90.

FIGS. 12 and 13 illustrate a case where four arm portions 290 extendforward from the first storage portion 48 a; a plane rear end 292 isformed at a leading end of the plate-like portion 162, opposite to thearm portions 290; and a plurality of bolts 294 are inserted into bores,not shown, longitudinally formed in the rear end 292, and threaded intothreaded holes, not shown, of the arm portions 290, therebylongitudinally coupling the plate-like portion 162 and the respectivearm portions 290 with the four bolts 294. This coupling in thelongitudinal direction in which the two-wheeled electric vehicle 10travels allows the realization of coupling capable of resisting shearforce (force applied in the longitudinal direction).

Although the present invention has been described by using the preferredembodiment, the technical scope of the present invention is not limitedto the scope described in the foregoing embodiment. It is obvious tothose skilled in the art that the foregoing embodiment may be variouslyaltered or improved. It will be apparent from the description of theappended claims that a form obtained by altering or improving theembodiment can also be included in the technical scope of the presentinvention.

1. An electric vehicle wherein an output of a motor is transmitted to anaxle through a reduction mechanism in order to rotate a wheel,comprising: a hollow cylindrical shaft forming the axle, said hollowcylindrical shaft passing substantially coaxially through the wheel in amanner extending from both sides of the wheel; a motor shaft insertedinto a hollow portion of the cylindrical shaft substantially coaxiallywith the cylindrical shaft in a manner extending from both ends of thecylindrical shaft; said motor being connected to a base end of the motorshaft extending from one end of the cylindrical shaft; said reductionmechanism being connected to a leading end of the motor shaft extendingfrom the other end of the cylindrical shaft; and a coupling portion forcoupling between the one end of the cylindrical shaft and the wheel, anda sealing portion for sealing between the wheel and the motor in amanner surrounding the coupling portion, said coupling portion and saidsealing portion being provided between the wheel and the motor.
 2. Theelectric vehicle according to claim 1, wherein the coupling portion iscomposed of a threaded portion formed at the one end of the cylindricalshaft; and a nut threaded onto the threaded portion for coupling betweenthe wheel and the cylindrical shaft.
 3. The electric vehicle accordingto claim 2, and further comprising: a motor case for storing the motor;and a first bearing inserted between the motor case and the wheel in amanner surrounding the motor shaft, the cylindrical shaft, and thecoupling portion, the first bearing relatively rotatably mounting themotor case to the wheel.
 4. The electric vehicle according to claim 3,wherein a portion of the motor case opposite the coupling portion istapered so as to deviate from the nut.
 5. The electric vehicle accordingto claim 3, and further comprising: a motor module composed of the motorand the motor case; a reduction mechanism module composed of thereduction mechanism and a reduction mechanism case for storing thereduction mechanism; and a second bearing inserted between the reductionmechanism case and the wheel in a manner surrounding the motor shaft andthe cylindrical shaft, the second bearing relatively rotatably mountingthe reduction mechanism case to the wheel.
 6. The electric vehicleaccording to claim 4, and further comprising: a motor module composed ofthe motor and the motor case; a reduction mechanism module composed ofthe reduction mechanism and a reduction mechanism case for storing thereduction mechanism; and a second bearing inserted between the reductionmechanism case and the wheel in a manner surrounding the motor shaft andthe cylindrical shaft, the second bearing relatively rotatably mountingthe reduction mechanism case to the wheel.
 7. The electric vehicleaccording to claim 5, wherein a labyrinth structure is formed betweenthe reduction mechanism case and the wheel in a manner surrounding thesecond bearing.
 8. The electric vehicle according to claim 7, andfurther comprising a brake for braking rotation of the wheel, whereinthe brake is disposed in a hollow portion between the labyrinthstructure provided between the reduction mechanism case and the wheel,and the second bearing.
 9. The electric vehicle according to claim 5,and further comprising a third bearing inserted between the motor caseand the motor shaft, the third bearing relatively rotatably supportingthe motor case on the motor shaft, wherein sealing is applied to atleast one of the first to third bearings.
 10. The electric vehicleaccording to claim 6, and further comprising a third bearing insertedbetween the motor case and the motor shaft, the third bearing relativelyrotatably supporting the motor case on the motor shaft, wherein sealingis applied to at least one of the first to third bearings.
 11. Theelectric vehicle according to claim 3, wherein the sealing portion is alabyrinth structure formed between the motor case and the wheel in amanner surrounding the first bearing, and/or the sealed first bearing.12. The electric vehicle according to claim 4, wherein the sealingportion is a labyrinth structure formed between the motor case and thewheel in a manner surrounding the first bearing, and/or the sealed firstbearing.
 13. The electric vehicle according to claim 2, wherein a holeportion or a bolt head is provided at the leading end of the motorshaft, the hole portion allowing insertion of a screw-driver or a hexwrench.
 14. The electric vehicle according to claim 3, wherein a holeportion or a bolt head is provided at the leading end of the motorshaft, the hole portion allowing insertion of a screw-driver or a hexwrench.
 15. The electric vehicle according to claim 2, wherein thereduction mechanism is provided with: a first gear formed at the leadingend of the motor shaft; a second gear disposed forwardly of the motorshaft, the second gear engaging with the first gear; a reduction shaftdisposed forwardly of and substantially parallel to the cylindricalshaft and the motor shaft, and substantially coaxially connected to thesecond gear; a third gear formed on the side of the reduction shafttoward the wheel; and a fourth gear substantially coaxially connected tothe cylindrical shaft on the other end of the cylindrical shaft, thefourth gear engaging with the third gear, wherein a hole portion or abolt head is provided at an end of the reduction shaft toward the secondgear, the hole portion allowing insertion of a screw-driver or a hexwrench.
 16. The electric vehicle according to claim 3, wherein thereduction mechanism is provided with: a first gear fainted at theleading end of the motor shaft; a second gear disposed forwardly of themotor shaft, the second gear engaging with the first gear; a reductionshaft disposed forwardly of and substantially parallel to thecylindrical shaft and the motor shaft, and substantially coaxiallyconnected to the second gear; a third gear formed on the side of thereduction shaft toward the wheel; and a fourth gear substantiallycoaxially connected to the cylindrical shaft on the other end of thecylindrical shaft, the fourth gear engaging with the third gear, whereina hole portion or a bolt head is provided at an end of the reductionshaft toward the second gear, the hole portion allowing insertion of ascrew-driver or a hex wrench.
 17. The electric vehicle according toclaim 1, wherein a sealing member is inserted between the other end ofthe cylindrical shaft and the motor shaft.
 18. The electric vehicleaccording to claim 1, and further comprising a double-sided swing armfor supporting the motor shaft, the cylindrical shaft, and the wheel byrespectively supporting the motor and the reduction mechanism.
 19. Anoutput for an electric vehicle comprising: an axle having a hollowcylindrical shaft, said hollow cylindrical shaft passing substantiallycoaxially through a wheel in a manner extending from both sides of thewheel; a motor shaft inserted into a hollow portion of the cylindricalshaft substantially coaxially with the cylindrical shaft in a mannerextending from a first end and a second end of the cylindrical shaft; amotor being connected to a base end of the motor shaft extending fromthe first end of the cylindrical shaft; a reduction mechanismoperatively connected to rotate the wheel, said reduction mechanismbeing connected to a leading end of the motor shaft extending from thesecond end of the cylindrical shaft; and a coupling portion for couplingbetween the first end of the cylindrical shaft and the wheel, and asealing portion for sealing between the wheel and the motor in a mannersurrounding the coupling portion.
 20. The electric vehicle according toclaim 19, wherein the coupling portion is composed of a threaded portionformed at the one end of the cylindrical shaft; and a nut threaded ontothe threaded portion for coupling between the wheel and the cylindricalshaft.